The headline on Michael Keaton's issue is "Michael Keaton is... Recedeljuice!", a reference to the film Beetlejuice which starred Keaton as Betelgeuse and also a reference to his receding hairline.
The abbreviation HRH, short for "Hair Royal Hairline", is a pun on the title "Her Royal Highness" (HRH).
The "Itchystan" flag is a parody of the Soviet Union, with the hammer and sickle being replaced with an axe and dynamite. A Soviet Union-like version of the theme song also plays.
Quirk Girl is a parody of the TV series New Girl. The characters Quirk Girl and Schultz are parodies of Jessica Day, played by Zooey Deschanel, and Schmidt, played by Max Greenfield. Both actors also voice their Simpsons parodies. The song played by Quirk Girl at the end is a parody of the theme song of the series.
Smiling Friends later responded to this by depicting a scene in the episode "Squim Returns" in which Pim watches a parody of The Simpsons, in which "Marge" asks "Blart" about what he's doing on his tablet, before "Blart" gets eaten by "Homer". Pim laughs, claiming that they're still funny after 487 seasons.
During the song sequence, Itchy grabs a lamppost while holding an umbrella, mimicking Gene Kelly's iconic moment in the 1952 musical Singin' in the Rain.
When Marge is worried that Bart and Lisa may stop speaking and drift apart, Homer makes an analogy to Sweet and CJ Johnson, the brothers from Grand Theft Auto: San Andreas. In the video game series, CJ Johnson is blamed by Sweet for the death of their brother Brian, a tragedy that drives the two apart.
Homer also mentions Los Santos, a fictional city from the game, and Big Smoke, a relevant character.
The next day, Homer plays the game on the TV.
The song heard when Homer wears the sunglasses and plays the video game is "Superbad" by Top Dogz, which is part of the soundtrack of the video game Watch Dogs: Legion.
The WNBA is called the NBA in the future while the NBA is called the MNBA, implying that the popularity of women's basketball will eventually surpass that of men's.
Bart bought a Chevrolet Camaro with the money he got from looking after the old people.
Comic Book Guy says the Camaro is as red as the planet Arrakis, saying it's a reference to Dune.
Bart has one of the t-shirts with him holding a slingshot ready to shoot with the text "Underachiever ('And proud of it, man!')", one of the popular real-life t-shirts created after "Bart Gets an "F"" and banned from schools.
The Disorient Express is a reference to the Orient Express.
When Bart mentions Itchy reanimating the corpse of Ty Cobb in a plot to "slide spikes first into Scratchy's face" he is alluding to Cobb's actual practice of sliding spikes high to inflict wounds on the covering baseman.
